Fix Span link to proc-macro2 documentation
diff --git a/src/keyword.rs b/src/keyword.rs
index b02cd1c..07ee1bd 100644
--- a/src/keyword.rs
+++ b/src/keyword.rs
@@ -29,7 +29,7 @@
 /// [Peeking]: parse/struct.ParseBuffer.html#method.peek
 /// [Parsing]: parse/struct.ParseBuffer.html#method.parse
 /// [Printing]: https://docs.rs/quote/0.6/quote/trait.ToTokens.html
-/// [`Span`]: struct.Span.html
+/// [`Span`]: https://docs.rs/proc-macro2/0.4/proc_macro2/struct.Span.html
 ///
 /// # Example
 ///
diff --git a/src/token.rs b/src/token.rs
index f8eb6b8..b03d335 100644
--- a/src/token.rs
+++ b/src/token.rs
@@ -86,7 +86,7 @@
 //! [Peeking]: ../parse/struct.ParseBuffer.html#method.peek
 //! [Parsing]: ../parse/struct.ParseBuffer.html#method.parse
 //! [Printing]: https://docs.rs/quote/0.6/quote/trait.ToTokens.html
-//! [`Span`]: ../struct.Span.html
+/// [`Span`]: https://docs.rs/proc-macro2/0.4/proc_macro2/struct.Span.html
 
 use std;
 #[cfg(feature = "extra-traits")]